特细砂混凝土的应用及其经济性

通过介绍特细砂混凝土在嘉陵江流域的马回、东西关、桐子壕等水电站建设中的应用情况 ,分析了特细砂混凝土的特性和配合比等特点 ,并闸明了在施工中使用特细砂混凝土的经济效益。     

绿色再生混凝土利用途径与评定思路

就再生混凝土骨料进行深入系统的研究 ,建立了一套与现行评价天然骨料标准相一致的评定方法 ,具有工程实际意义 ,为将来实际应用作好了基础理论研究     

Profile-Based Linguistic Uniformity as a Generic Method for Comparing Language Varieties

In this text we present``profile-based linguistic uniformity', a methoddesigned to compare language varieties on thebasis of a wide range of potentiallyheterogeneous linguistic variables. In manyrespects a parallel can be drawn with currentmethods in dialectometry (for an overview, see,Nerbonne and Heeringa, 2001; Heeringa, Nerbonneand Kleiweg, 2002): in both casesdissimilarities between varieties on the basisof individual variables are summarized inglobal dissimilarities, and a series oflanguage varieties are subsequently clusteredor charted using multivariate techniques suchas cluster analysis or multidimensionalscaling. This global similarity between themethods makes it possible to compare them andto investigate the implications of notabledifferences. In this text we specifically focuson, and defend one characteristic of ourmethodology, its profile-based nature.     

Influence of aggregate content on the migration coefficient of concrete materials using electrochemical method

In order to investigate the effect of coarse aggregate content on the chloride ion migration coefficient of concrete, specimens with different coarse aggregate volume fractions and two water/cement (w/c) ratios of mortar matrix were used. The chloride ion migration coefficient of concrete is obtained using the electrochemical technique to accelerate chloride ion migration in cement-based material and the experimental results were plotted as a function of the fine aggregate volume fraction. The results are analyzed comparing experimental results and theoretical models that represent the concretes as three-phase composite materials. The three phases are the mortar matrix, the coarse aggregate, and the interfacial transition zone between the two. The chloride ion migration coefficient is used to assess the dilution, tortuosity, interfacial transition zone (ITZ) and, percolation effects of coarse aggregate in concrete. It appears that the dilution and tortuosity effects are a dominant factor affecting the chloride ion migration coefficient of concrete in the low volume fraction of coarse aggregate. As the volume fraction of coarse aggregate increases to 40 and 20% in concrete of w/c ratio 0.35 and 0.45, respectively, the ITZ with percolation effects are significantly.     

海水冻融后轻骨料混凝土的双轴压压强度和变形性能

针对我国渤海湾北部海域轻骨料混凝土结构的工作环境和受力状态，进行了海水中不同冻融循环次数后轻骨料混凝土的双轴压压强度试验，考察了试件的破坏形态和表面裂缝的走向特征。根据试验结果，分析了极限抗压强度随冻融循环次数和应力比的变化规律，并在此基础上建立了考虑海水冻融影响的双轴压压强度准则。探讨了冻融循环作用后轻骨料混凝土的双轴压压变形性能，包括峰值应变、应力-应变关系随冻融循环次数和应力比的变化规律。研究结果说明，随冻融循环次数的增加各种应力比下的应力-应变关系曲线均逐渐扁平，峰值应力点明显下降并右移，说明混凝土的极限抗压强度逐渐降低。     

混凝土骨料二维分布的模拟和应用

通过在一个矩形截面上模拟混凝土骨料的实际分布，获得了该截面上任一点的骨料分布密度和骨料分布的统计特性。模拟结果表明，当模拟次数趋向于无穷大时，截面上任一点的骨料分布密度趋向于定值，对于不同的骨料面积百分数，骨料分布密度曲线的形状十分相似，均由上升段和水平段两部分组成。基于这些模拟结果，利用数学拟合获得了骨料分布密度的解析表达式，并被混凝土实验所初步证实。作为一个应用，本文计算了混凝土截面上各点的氯离子扩散系数。     

Porosity of recycled concrete with substitution of recycled concrete aggregate: An experimental study

In this paper, we present the experimental analysis of samples of recycled concrete (RC) with replacement of natural aggregate (NA) by recycled aggregate originating from concrete (RCA). The results of the tests of mechanical properties of RC were used for comparison with tests of mercury intrusion porosimetry (MIP), in which the distribution of the theoretical pore radius, critical pore ratio, the surface area of the concrete, threshold ratio and average pore radius were studied at ages of 7, 28 and 90 days. The results showed some variation in the properties of the RC with respect to ordinary concrete. Porosity increases considerably when NA is replaced by RCA. Additionally, a reduction in the mechanical properties of the RC is seen compared with ordinary concrete when porosity increases.     

Breaking of structural dormancy in seeds of Tetrapleura tetraptera by Aspergillus niger

Aspergillus niger (strain UUF9202) significantly reduced the dormancy period and boosted aggregate germination percentage (AGP) in seeds of Tetrapleura tetraptera. A net reduction in mean germination time (MGT) to 12 days and an increase from 0 to 42% AGP were obtained in 32 days. The optimal spore inoculum of the fungus was 8.5 × 10≥10 ml^?1 per 100 seeds in 96 h pregermination incubation. The potential of some physical factors in combination with this fungal concentration in enhancing AGP was evaluated. The treatments were as follows: (i) hot water scarification at 30°C, 50°C, 80°C and 100°C plus A niger; and (ii) nicking by decoating at either the micropylar or chalazal ends plus A niger. Micropylar scarification plus A niger gave the highest AGP (94%) followed by chalazal scarification plus A niger (86%) and hot water dip at 80°C + A niger (82%). The control seeds which were soaked in presterilised (by autoclaving at 121°C for 15 min) A niger spore suspension at 30°C gave zero germination.     

砖烟囱集团装药定向爆破拆除

对一座 40 m 高的砖烟囱,采用TNT集团装药实施定向倒塌拆除爆破.介绍了该烟囱拆除爆破工艺技术,爆破参数和施工方法.     

Effect of sillimanite beach sand composition on mullitization and properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

Mullite was developed by reaction sintering of sillimanite beach sand and calcined alumina. Two varieties of sillimanite beach sand viz. S and Z having different compositions were selected. Synthesis and properties of mullite were very much dependent on the sillimanite beach sand composition. Presence of higher amount of impurities in the Z-variety of sillimanite sand favours the densification by liquid phase formation. Presence of zircon in Z-variety increases the hardness and fracture toughness. Alumina addition improves the mechanical/thermomechanical properties of the samples. Mullite retains the usual orthorhombic habit of sillimanite. Rounded to sub rounded zirconia dispersed within the mullite matrix of the sample ZA is noticed.